U.S. patent application number 13/122200 was filed with the patent office on 2011-09-08 for electric distance meter.
Invention is credited to Kunihiro Hayashi, Ikuo Ishinabe.
Application Number | 20110216305 13/122200 |
Document ID | / |
Family ID | 42073410 |
Filed Date | 2011-09-08 |
United States Patent
Application |
20110216305 |
Kind Code |
A1 |
Hayashi; Kunihiro ; et
al. |
September 8, 2011 |
ELECTRIC DISTANCE METER
Abstract
An electric distance meter is downsized by using a condensing
optical member having a small outer diameter (effective diameter)
as a condensing optical member in a light-receiving optical system
of reflection light from an object, reducing a focal length of the
condensing optical member without reducing a spread angle to a
light-receiving optical fiber and reducing a diameter of the
light-receiving optical fiber. An optical distance meter 10 emits
outgoing light E from a light source 15 to an object, and receives
reflection light R from the object by a light receiver 22, so as to
perform distance measurement. The optical distance meter 10
includes an emitting optical system which irradiates the object by
the emission light E via an objective lens 26 and a light-receiving
optical system which guides the reflection light R via the
objective lens 26 to the light receiver 22, and a cone prism 34
which changes a cross-section shape of a light beam without
generating a transmission deflection angle is provided on an
optical axis of the light-receiving optical system or an optical
axis of the emission optical system.
Inventors: |
Hayashi; Kunihiro; (Tokyo,
JP) ; Ishinabe; Ikuo; (Tokyo, JP) |
Family ID: |
42073410 |
Appl. No.: |
13/122200 |
Filed: |
September 24, 2009 |
PCT Filed: |
September 24, 2009 |
PCT NO: |
PCT/JP2009/066495 |
371 Date: |
May 10, 2011 |
Current U.S.
Class: |
356/4.01 |
Current CPC
Class: |
G01S 7/4813 20130101;
G01S 17/08 20130101; G01S 7/4818 20130101 |
Class at
Publication: |
356/4.01 |
International
Class: |
G01C 3/08 20060101
G01C003/08 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 3, 2008 |
JP |
2008-258732 |
Claims
1. An electric distance meter, which emits outgoing light from a
light source toward an object, and measures a distance by receiving
reflection light of the outgoing light from the object by a light
receiver, comprising: an emission optical system configured to
irradiate the object by the outgoing light via an objective lens; a
light-receiving optical system configured to guide the reflection
light to the light receiver via the objective lens; and a cone
prism configured to change a cross-section shape of a light beam
without generating a transmission deflection angle, the cone prism
being provided on an optical path of the light-receiving optical
system or an optical path of the emission optical system.
2. The electric distance meter according to claim 1, wherein a
reflection light collimator optical member configured to convert
the reflection light into a substantial parallel light beam and a
condensing optical member configured to condense the reflection
light via the reflection light collimator optical member are
provided in an optical path from the objective lens to the light
receiver, and the cone prism configured to change the cross-section
shape of the light beam while reducing an outer diameter of the
light beam without generating the transmission deflection angle is
provided between the reflection light collimator optical member and
the condensing optical member.
3. The electric distance meter according to claim 1, wherein the
outgoing light is emitted via the objective lens on an irradiation
optical axis toward the object, and the reflection light of the
outgoing light from the object entered onto the object lens is
received in a state without having a central portion, which
circularly surrounds the outgoing light, a reflection light
collimator optical member configured to convert the reflection
light into a parallel light beam and a condensing optical member
configured to condense the reflection light via the reflection
light collimator optical member arc provided in an optical path
from the objective lens to the light receiver, and the cone prism
configured to convert the reflection light without having a central
potion, which is converted into a parallel light beam via the
reflection light collimator optical member, into a parallel light
beam having the central portion by changing the cross-section shape
of a light beam while reducing an outer diameter of the light beam
without generating a transmission deflection angle is provided
between the reflection light collimator optical member and the
condensing optical member.
4. An electric distance meter, which measures a distance to an
object, comprising: a light receiving and emitting mechanism
configured to emit light from a light source and receive light by a
light receiver; an optical path forming optical system configured
to form an emission optical path which emits outgoing light from
the light receiving and emitting mechanism from an objective lens
on an irradiation optical axis toward the object and form a
reflection optical path which guides reflection light of the
outgoing light from the object entered onto the objective lens to
the light receiving and emitting mechanism in a sate without having
a central portion, which circularly surrounds the outgoing light;
an emitting optical fiber configured to connect the light receiving
and emitting mechanism and the optical path forming optical system,
and guide the outgoing light emitted from the light receiving and
emitting mechanism to the emission optical path of the optical path
forming optical system; and a light-receiving optical fiber
configured to connect the light receiving and emitting mechanism
and the optical path forming optical system, and guide the
reflection light via the reflection optical path of the optical
path forming optical system to the light receiver of the light
receiving and emitting mechanism, wherein the reflection optical
path includes a reflection light collimator optical member
configured to convert the reflection light into a substantial
parallel light beam and a condensing optical member configured to
condense the reflection light via the reflection light collimator
optical member to be entered onto an incident end face of the
light-receiving optical fiber, and a cone prism configured to
change a cross-section shape of a light beam while reducing an
outer diameter of the light beam without generating a transmission
deflection angle is provided between the reflection light
collimator optical member and the condensing light optical
member.
5. The electric distance meter according to claim 4, wherein the
cone prism converts the reflection light without having a central
portion, which is converted into a parallel light beam via the
reflection light collimator optical member, into a parallel light
beam having the central portion by deflecting the reflection light
without having the central portion on an optical axis side in a
radial direction.
6. The electric distance meter according to claim 2, wherein the
cone prism includes a rotationally symmetric cylindrical shape
having an optical axis from the reflection light collimator optical
member to the condensing optical member as a symmetrical axis, an
end face located on the reflection light collimator optical member
side includes a conical shape projecting toward the reflection
light collimator optical member, an end face located on the
condensing optical member side includes a conical shape having a
concave shape to the condensing optical member, and facing portions
of the end face located on the condensing optical member side and
the end face located on the reflection light collimator optical
member side in a radial direction with the symmetrical axis at the
center are parallel.
7. The electric distance meter according to claim 1, wherein an
outgoing light collimator optical member configured to convert the
outgoing light into a substantial parallel light beam is provided
in an optical path from the light source to the objective lens, and
the cone prism configured to convert the outgoing light of the
parallel light beam via the outgoing light collimator optical
member into a parallel light beam without having a central portion
by changing a cross-section shape of a light beam while increasing
an outer diameter of the light beam without generating a
transmission deflection angle is provided between the outgoing
light collimator optical member and the objective lens.
8. The electric distance meter according to claim 1, wherein the
outgoing light is emitted via the objective lens to circularly
surround an irradiation optical axis toward the object, and the
reflection light from the object entered onto the objective lens
near the irradiation optical axis to be surrounded by the outgoing
light is received by the light receiver, an outgoing light
collimator optical member configured to convert the outgoing light
into a substantial parallel light is provided in an optical path
from the light source to the objective lens, and the cone prism
configured. to convert the outgoing light via the outgoing light
collimator optical member into a parallel light beam without having
a central portion by changing a cross-section shape of a light beam
while increasing an outer diameter of the light beam without
generating a transmission deflection angle is provided between the
outgoing light collimator optical member and the objective
lens.
9. An electric distance meter, which measures a distance to an
object, comprising: a light receiving and emitting mechanism
configured to emit light from a light source and receive light by a
light receiver; an optical path forming optical system configured
to form an emission optical path which emits via the objective lens
outgoing light from the light receiving and emitting mechanism to
surround an irradiation optical axis toward the object, and to form
a reflection optical path which guides the reflection light from
the object entered onto the objective lens near the irradiation
optical axis to be surrounded by the outgoing light to the light
emitting and receiving mechanism; an emitting optical fiber
configured to connect the light receiving and emitting optical
mechanism and the optical path forming optical system and guide the
outgoing light emitted from the light receiving and emitting
mechanism to the emission optical path of the emission optical
system; a light-receiving optical fiber configured to connect the
light receiving and emitting optical mechanism and the optical path
forming optical system and guide the reflection light via the
reflection optical path of the light receiving optical system to
the light receiver of the light receiving and emitting mechanism,
wherein the emission optical path includes an outgoing light
collimator optical member configured to convert the emission light
into a parallel light beam, and the cone prism configured to
convert the emission light via the outgoing light collimator
optical member into a parallel light beam without having a central
portion by changing a cross-section shape of the light beam while
increasing an outer diameter of the light beam without generating a
transmission deflection angle is provided between the outgoing
light collimator optical member and the objective lens.
10. The electric distance meter according to claim 9, wherein the
cone prism IS configured to convert the emission light converted
into a parallel light beam via the outgoing light collimator
optical member into a parallel light beam without having the
central portion by deflecting in a radial direction which is the
direction opposite to an optical axis.
11. The electric distance meter according to claim 7, wherein the
cone prism includes a rotationally symmetric cylindrical shape
having an optical axis from the outgoing light collimator optical
member to the objective lens as a symmetrical axis, an end face
located on the outgoing light collimator optical member side
includes a conical shape having a concave shape to the outgoing
light collimator optical member, an end face located on the
objective lens side includes a conical shape projecting toward the
objective lens, facing portions of the end face located on the
objective lens side and the end face located on the outgoing light
collimator optical member side in a radial direction with the
symmetrical axis at the center are parallel.
12. The electric distance meter according to claim 3, wherein the
cone prism includes a rotationally symmetric cylindrical shape
having an optical axis from the reflection light collimator optical
member to the condensing optical member as a symmetrical axis, an
end face located on the reflection light collimator optical member
side includes a conical shape projecting toward the reflection
light collimator optical member, an end face located on the
condensing optical member side includes a conical shape having a
concave shape to the condensing optical member, and facing portions
of the end face located on the condensing optical member side and
the end face located on the reflection light collimator optical
member side in a radial direction with the symmetrical axis at the
center are parallel.
13. The electric distance meter according to claim 4, wherein the
cone prism includes a rotationally symmetric cylindrical shape
having an optical axis from the reflection light collimator optical
member to the condensing optical member as a symmetrical axis, an
end face located on the reflection light collimator optical member
side includes a conical shape projecting toward the reflection
light collimator optical member, an end face located on the
condensing optical member side includes a conical shape having a
concave shape to the condensing optical member, and facing portions
of the end face located on the condensing optical member side and
the end face located on the reflection light collimator optical
member side in a radial direction with the symmetrical axis at the
center are parallel.
14. The electric distance meter according to claim 5, wherein the
cone prism includes a rotationally symmetric cylindrical shape
having an optical axis from the reflection light collimator optical
member to the condensing optical member as a symmetrical axis, an
end face located on the reflection light collimator optical member
side includes a conical shape projecting toward the reflection
light collimator optical member, an end face located on the
condensing optical member side includes a conical shape having a
concave shape to the condensing optical member, and facing portions
of the end face located on the condensing optical member side and
the end face located on the reflection light collimator optical
member side in a radial direction with the symmetrical axis at the
center are parallel.
15. The electric distance meter according to claim 8, wherein the
cone prism includes a rotationally symmetric cylindrical shape
having an optical axis from the outgoing light collimator optical
member to the objective lens as a symmetrical axis, an end face
located on the outgoing light collimator optical member side
includes a conical shape having a concave shape to the outgoing
light collimator optical member, an end face located on the
objective lens side includes a conical shape projecting toward the
objective lens, facing portions of the end face located on the
objective lens side and the end face located on the outgoing light
collimator optical member side in a radial direction with the
symmetrical axis at the center are parallel.
16. The electric distance meter according to claim 9, wherein the
cone prism includes a rotationally symmetric cylindrical shape
having an optical axis from the outgoing light collimator optical
member to the objective lens as a symmetrical axis, an end face
located on the outgoing light collimator optical member side
includes a conical shape having a concave shape to the outgoing
light collimator optical member, an end face located on the
objective lens side includes a conical shape projecting toward the
objective lens, facing portions of the end face located on the
objective lens side and the end face located on the outgoing light
collimator optical member side in a radial direction with the
symmetrical axis at the center are parallel.
17. The electric distance meter according to claim 10, wherein the
cone prism includes a rotationally symmetric cylindrical shape
having an optical axis from the outgoing light collimator optical
member to the objective lens as a symmetrical axis, an end face
located on the outgoing light collimator optical member side
includes a conical shape having a concave shape to the outgoing
light collimator optical member, an end face located on the
objective lens side includes a conical shape projecting toward the
objective lens, facing portions of the end face located on the
objective lens side and the end face located on the outgoing light
collimator optical member side in a radial direction with the
symmetrical axis at the center are parallel.
Description
TECHNICAL FIELD
[0001] The present invention relates to an electric distance meter
which measures a distance by using light, in particular, to an
electric distance meter which irradiates an object on an outgoing
optical axis by outgoing light via an objective lens, and obtains
reflection light on the outgoing optical axis via the objective
lens.
BACKGROUND ART
[0002] An electric distance measuring method, which measures a
distance based on outgoing light toward an object and reflection
light of the outgoing light by the object received by a light
receiver, is known in surveying with public works, for example. In
an electric distance meter which performs such a method, the same
objective lens is used in the outgoing optical path to the object
and the reflection optical path from the object (for example, refer
to Patent Document 1). In such an electric distance meter, in the
optical path passing through the objective lens facing the object,
the central area including the optical axis is used as the outgoing
optical path and the circumferential area thereof is used as the
reflection optical path.
PRIOR ART DOCUMENT
Patent Document
[0003] Document 1: Japanese Unexamined Patent Application
Publication No. 2004-69611
DISCLOSURE OF THE INVENTION
Problems To Be Solved By the Invention
[0004] However, in the above electric distance meter, the
reflection optical path is set in the circumferential area, so that
it is necessary for the reflection light via the reflection optical
path not to have a light beam in the central portion. A condensing
lens (condensing optical member) for receiving reflection light by
a light receiver is generally used in an electric distance meter.
Accordingly, it is necessary to use a condensing lens having a
large diameter (effective diameter) relative to a large-outer
diameter reflection light without having a light beam in the
central portion, so that it becomes difficult to downsize the
electric distance meter.
[0005] Moreover, the electric distance meter can be downsized by
reducing the distance between the condensing lens and the light
receiver. In this case, in order to reduce the distance between the
condensing lens and the light receiver, i.e., in order to reduce
the focal length of the condensing lens, it is necessary to use a
condensing lens having a large NA (numerical aperture stop).
However, if a diameter (effective diameter) of a lens is large, it
is difficult to set a large NA compared to a small diameter
(effective diameter) lens, and it is difficult to reduce the focal
length of the condensing lens.
Means For Solving the Problems
[0006] It is, therefore, an object of the present invention to
provide a downsized electric distance meter by using a condensing
optical member having a small outer diameter (effective diameter)
as a condensing optical member in a light receiving optical system
of reflection light from an object, and by reducing a focal length
of the condensing optical member without reducing a spread angle to
a light-receiving optical fiber, so as to reduce a diameter of the
light-receiving optical fiber.
[0007] An electric distance meter of the present invention, which
emits outgoing light from a light source toward an object, and
measures a distance by receiving reflection light of the outgoing
light from the object by a light receiver, includes an emission
optical system configured to irradiate the object by the outgoing
light via an objective lens, a light-receiving optical system
configured to guide the reflection light to the light receiver via
the objective lens, and a cone prism configured to change a
cross-section shape of a light beam without generating a
transmission deflection angle, the cone prism being provided on an
optical path of the light-receiving optical system or an optical
path of the emission optical system.
[0008] Preferably, a reflection light collimator optical member
configured to convert the reflection light into a substantial
parallel light beam and a condensing optical member configured to
condense the reflection light via the reflection light collimator
optical member are provided in an optical path from the objective
lens to the light receiver, and the cone prism configured to change
the cross-section shape of the light beam while reducing an outer
diameter of the light beam without generating the transmission
deflection angle is provided between the reflection light
collimator optical member and the condensing optical member.
[0009] Preferably, the outgoing light is emitted via the objective
lens on an irradiation optical axis toward the object, and the
reflection light of the outgoing light from the object entered onto
the object lens is received in a state without having a central
portion, which circularly surrounds the outgoing light, a
reflection light collimator optical member configured to convert
the reflection light into a parallel light beam and a condensing
optical member configured to condense the reflection light via the
reflection light collimator optical member are provided in an
optical path from the objective lens to the light receiver, and the
cone prism configured to convert the reflection light without
having a central potion, which is converted into a parallel light
beam via the reflection light collimator optical member, into a
parallel light beam having the central portion by changing the
cross-section shape of a light beam while reducing an outer
diameter of the light beam without generating a transmission
deflection angle is provided between the reflection light
collimator optical member and the condensing optical member.
[0010] An electric distance meter of the present invention, which
measures a distance to an object, includes a light receiving and
emitting mechanism configured to emit light from a light source and
receive light by a light receiver, an optical path forming optical
system configured to form an emission optical path which emits
outgoing light from the light receiving and emitting mechanism from
an objective lens on an irradiation optical axis toward the object
and form a reflection optical path which guides reflection light of
the outgoing light from the object entered onto the objective lens
to the light receiving and emitting mechanism in a sate without
having a central portion, which circularly surrounds the outgoing
light, an emitting optical fiber configured to connect the light
receiving and emitting mechanism and the optical path forming
optical system, and guide the outgoing light emitted from the light
receiving and emitting mechanism to the emission optical path of
the optical path forming optical system, and a light-receiving
optical fiber configured to connect the light receiving and
emitting mechanism and the optical path forming optical system, and
guide the reflection light via the reflection optical path of the
optical path forming optical system to the light receiver of the
light receiving and emitting mechanism, wherein the reflection
optical path includes a reflection light collimator optical member
configured to convert the reflection light into a substantial
parallel light beam and a condensing optical member configured to
condense the reflection light via the reflection light collimator
optical member to be entered onto an incident end face of the
light-receiving optical fiber, and a cone prism configured to
change a cross-section shape of a light beam while reducing an
outer diameter of the light beam without generating a transmission
deflection angle is provided between the reflection light
collimator optical member and the condensing light optical
member.
[0011] Preferably, the cone prism converts the reflection light
without having a central portion, which is converted into a
parallel light beam via the reflection light collimator optical
member, into a parallel light beam having the central portion by
deflecting the reflection light without having the central portion
on an optical axis side in a radial direction.
[0012] Preferably, the cone prism includes a rotationally symmetric
cylindrical shape having an optical axis from the reflection light
collimator optical member to the condensing optical member as a
symmetrical axis, an end face located on the reflection light
collimator optical member side includes a conical shape projecting
toward the reflection light collimator optical member, an end face
located on the condensing optical member side includes a conical
shape having a concave shape to the condensing optical member, and
facing portions of the end face located on the condensing optical
member side and the end face located on the reflection light
collimator optical member side in a radial direction with the
symmetrical axis at the center are parallel.
[0013] Preferably, an outgoing light collimator optical member
configured to convert the outgoing light into a substantial
parallel light beam is provided in an optical path from the light
source to the objective lens, and the cone prism configured to
convert the outgoing light of the parallel light beam via the
outgoing light collimator optical member into a parallel light beam
without having a central portion by changing a cross-section shape
of a light beam while increasing an outer diameter of the light
beam without generating a transmission deflection angle is provided
between the outgoing light collimator optical member and the
objective lens.
[0014] Preferably, the outgoing light is emitted via the objective
lens to circularly surround an irradiation optical axis toward the
object, and the reflection light from the object entered onto the
objective lens near the irradiation optical axis to be surrounded
by the outgoing light is received by the light receiver, an
outgoing light collimator optical member configured to convert the
outgoing light into a substantial parallel light is provided in an
optical path from the light source to the objective lens, and the
cone prism configured to convert the outgoing light via the
outgoing light collimator optical member into a parallel light beam
without having a central portion by changing a cross-section shape
of a light beam while increasing an outer diameter of the light
beam without generating a transmission deflection angle is provided
between the outgoing light collimator optical member and the
objective lens.
[0015] An electric distance meter of the present invention, which
measures a distance to an object, includes a light receiving and
emitting mechanism configured to emit light from a light source and
receive light by a light receiver, an optical path forming optical
system configured to form an emission optical path which emits via
the objective lens outgoing light from the light receiving and
emitting mechanism to surround an irradiation optical axis toward
the object, and to form a reflection optical path which guides the
reflection light from the object entered onto the objective lens
near the irradiation optical axis to be surrounded by the outgoing
light to the light emitting and receiving mechanism, an emitting
optical fiber configured to connect the light receiving and
emitting optical mechanism and the optical path forming optical
system and guide the outgoing light emitted from the light
receiving and emitting mechanism to the emission optical path of
the emission optical system, a light-receiving optical fiber
configured to connect the light receiving and emitting optical
mechanism and the optical path forming optical system and guide the
reflection light via the reflection optical path of the light
receiving optical system to the light receiver of the light
receiving and emitting mechanism, wherein the emission optical path
includes an outgoing light collimator optical member configured to
convert the emission light into a parallel light beam, and the cone
prism configured to convert the emission light via the outgoing
light collimator optical member into a parallel light beam without
having a central portion by changing a cross-section shape of the
light beam while increasing an outer diameter of the light beam
without generating a transmission deflection angle is provided
between the outgoing light collimator optical member and the
objective lens.
[0016] Preferably, the cone prism is configured to convert the
emission light converted into a parallel light beam via the
outgoing light collimator optical member into a parallel light beam
without having the central portion by deflecting in a radial
direction which is the direction opposite to an optical axis.
[0017] Preferably, the cone prism includes a rotationally symmetric
cylindrical shape having an optical axis from the outgoing light
collimator optical member to the objective lens as a symmetrical
axis, an end face located on the outgoing light collimator optical
member side includes a conical shape having a concave shape to the
outgoing light collimator optical member, an end face located on
the objective lens side includes a conical shape projecting toward
the objective lens, facing portions of the end face located on the
objective lens side and the end face located on the outgoing light
collimator optical member side in a radial direction with the
symmetrical axis at the center are parallel.
Effect of the Invention
[0018] According to the electric distance meter of the present
invention, the condensing optical member in the light-receiving
optical system of the reflection light from the object condenses
the reflection light in which the diameter is reduced by the cone
prism. For this reason, a condensing optical member having a small
outer diameter (effective diameter) can be used.
[0019] According to the electric distance meter of the present
invention, since a condensing lens having a small outer diameter
(effective diameter) can be used as the condensing optical member
in the light-receiving optical system of the reflection light from
the object, compared to a conventional electric distance meter, the
diameter of the light-receiving optical fiber can be reduced by
decreasing the focal length of the condensing optical member
without decreasing a spread angle to the light-receiving optical
fiber.
[0020] Therefore, according to the electric distance meter of the
present invention, the size can be easily reduced.
Modes For Carrying Out the Invention
[0021] Hereinafter, an electric distance meter according to an
embodiment of the present invention will be described with
reference to the drawings.
EMBODIMENT
[0022] FIG. 1 is a schematic view illustrating an optical system of
an electric distance meter 10 according to the present invention.
FIG. 2 is a perspective view illustrating a cone prism 34
describing functions of the cone prism 34 for use in the electric
distance meter 10. FIG. 3 is a sectional view illustrating the cone
prism 34 including the optical axis (reflection optical axis Lr')
describing the functions of the cone prism 34.
[0023] The electric distance meter (EDM) 10 emits light (outgoing
light) toward an object to be measured, receives reflection light
reflected by the object and measures a phase difference and/or a
time difference from the emitting of the outgoing light to the
receiving of the reflection light, so as to measure a distance (not
shown). In the electric distance meter 10 of the present
embodiment, as illustrated in FIG. 1, a light receiving and
emitting mechanism 11 and an optical path forming optical system 12
are optically connected via an emission optical fiber 13 and a
light-receiving optical fiber 14.
[0024] The light receiving and emitting mechanism 11 emits outgoing
light E from a light source 15, and receives the reflection light R
by a light-receiving element 22 (light receiver), in order to
measure the phase difference and/or the time difference from the
emitting of the outgoing light E to the receiving of the reflection
light R. The optical path forming optical system 12 connected to
the light receiving and emitting mechanism 11 forms an emission
optical path which emits the outgoing light E along an irradiation
optical axis Li from an objective lens group 26 toward an object
(not shown), and forms a reflection optical path which receives the
reflection light R along the irradiation optical axis Li from the
object via the objective lens group 26.
[0025] The light emitting and receiving mechanism 11 includes the
light source 15, a first collimator lens 16, a first half mirror
17, a first condensing lens 18, and a first ND (Neutral Density)
filter device 19. The light source 15 emits light in which a phase
and intensity are appropriately adjusted under the control of a
controller (not shown). In this embodiment, a pulse laser diode is
used as the light source 15. The first collimator lens 16, the
first half mirror 17, the first condensing lens 18 and the first ND
filter device 19 are arranged on an outgoing optical axis Le of the
light source 15.
[0026] The first collimator lens 16 converts the outgoing light E
from the light source 15 into a light beam parallel to the outgoing
optical axis Le. The first half mirror 17 transmits a part of the
parallel light beam and reflects the remaining portion of the
parallel light beam to the light-receiving element 22.
[0027] The first condensing lens 18 is provided to condense the
outgoing light E which has transmitted the first half mirror 17.
The first condensing lens 18 condenses the outgoing light E which
has transmitted the first half mirror 17, and enters the outgoing
light E onto an incident end face 13a of the emission optical fiber
13 provided on the outgoing optical axis Le. The first ND filter
device 19 is provided between the incident end face 13a and the
first condensing lens 18.
[0028] The ND filter device 19 includes a discoid ND filter portion
1 9a and a motor 19b which rotates the ND filter portion 19a. The
ND filter portion 19a is a filter member in which the transmittance
is gradually changed according to an angular position from a
reference point, The first ND filter 19 is provided such that a
part of the ND filter portion 19a is located on the outgoing
optical axis Le. The light volume which enters onto the incident
end face 13a of the emission optical fiber 13 is adjusted by
driving the motor 19b under the control of a controller (not
shown). The outgoing light E entered onto this incident end face
13a is guided to the optical path forming optical system 12 via the
emission optical fiber 13, and is guided on the irradiation optical
axis Li for irradiating the not shown object as described
below.
[0029] The light receiving and emitting mechanism 11 includes a
second half mirror 20, a second condensing lens 21 and a
light-receiving element 22 in the reflection direction (on the
reflection optical axis Lr) by the first half mirror 17. The light
receiving and emitting mechanism 11 also includes a second
collimator lens 23, a noise elimination filter 24 and an emission
end face 14a of the light-receiving optical fiber 14 in the
reflection direction of the second half mirror 20 to the reflection
optical axis Lr as seen from the light-receiving element 22
side.
[0030] As described below, the reflection light R from the object
(not shown) is guided to the light-receiving optical fiber 14 by
the optical path forming optical system 12. The reflection light R
is emitted from the emission end face 14a of the light-receiving
optical fiber 14. The noise elimination filter 24, the second
collimator lens 23, the second half mirror 20, the second
condensing lens 21 and the light-receiving element 22 are provided
in order to receive the reflection light R. The axis line from the
emission end face 14a to the light receiving element 22 via the
second half mirror 20 is a light-receiving optical axis Lg.
[0031] The second collimator lens 23 converts the reflection light
R emitted from the emission end face 14a into a light beam parallel
to the receiving optical axis Lg. The second half mirror 20
reflects this reflection light R toward the second condensing light
21 and transmits the remaining portion of the outgoing light E
reflected by the first half mirror 17.
[0032] The second condensing lens 21 is provided to condense the
reflection light R reflected by the second half mirror 20 and the
outgoing light E which has transmitted the second half mirror 20.
The second condensing lens 21 condenses the reflection light R and
the outgoing light E such that the reflection light R and the
outgoing light E enters onto the light-receiving face 22a of the
light-receiving element 22.
[0033] A second ND filter device 25 is arranged between the second
half mirror 20 and the first half mirror 17. This second ND filter
device 25 has a configuration which is similar to that of the first
ND filter device 19. The rotation position of an ND filter portion
25a is adjusted according to the driving of a motor 25b under the
control of a controller (not shown), so that the volume of the
outgoing light E which is reflected by the first half mirror 17
toward the light-receiving face 22a of the light-receiving element
22 is adjusted. In this second ND filter device 25, the adjustment
volume is appropriately controlled according to the adjustment
volume in the first ND filter device 19.
[0034] The light-receiving element 22 to which the reflection light
R and the outgoing light E having the adjusted light volume are
guided outputs electric signals according to the light volume if
light enters onto the light-receiving face 22a. In this embodiment,
an APD (Avalanche Photodiode) is used as the light-receiving
element 22.
[0035] In the electric distance meter 10, by detecting a phase
difference between the outgoing light E emitted from the light
source 15, reflected by the first half mirror 17, and received by
the light-receiving element 22 and the reflection light R received
by the light-receiving element 22 via the optical path forming
optical system 12 and the initial phase of the outgoing light E, or
a time difference from the emitting of the outgoing light E to the
receiving of the reflection light R, a not shown calculator
calculates a distance from the electric distance meter 10 to the
object (not shown), so as to perform distance measurement.
[0036] The optical path forming optical system 12 is optically
connected to the light receiving and emitting mechanism 11 via the
emission optical fiber 13 and the light-receiving optical fiber
14.
[0037] This optical path forming optical system 12 emits the
outgoing light E guided by the emission optical fiber 13 along the
irradiation optical axis Li, and has the objective lens group 26 on
the irradiation optical path Li. The optical path forming optical
system 12 includes on the outgoing optical path Le' of the emission
end face 13b of the emission optical fiber 13 a third collimator
lens 27, an expander lens 28 and a first mirror 29. The optical
path forming optical system 12 also includes a double-sided mirror
30 in the reflection direction to the emission optical axis Le' in
the first mirror 29. This double-sided mirror 30 is in the form of
plates having reflection surfaces (first reflection face 30a and
second reflection face 30b) on both surfaces. In this embodiment,
the double-sided mirror 30 is a discoid. The first reflection face
30a is disposed on the first mirror 29 side. The double-sided
mirror 30 is provided such that the reflection direction of the
first reflection mirror 30a corresponds to the irradiation optical
axis Li.
[0038] The third collimator lens 27 converts the outgoing light E
emitted from the emission end face 13b of the emission optical
fiber 13 into a light beam parallel to the outgoing optical axis
Le'. The expander lens 28 converts the outgoing light E converted
into the parallel light beam by the third collimator lens 27 into
an increased light beam in which the beam diameter is increased.
The first mirror 29 reflects the outgoing light E converted into
the increased light beam by the expander lens 28 toward the first
reflection face 30a of the double-sided mirror 30. This first
reflection face 30a reflects the outgoing light E toward the
objective lens group 26. This objective lens group 26 emits the
increased outgoing light E on the irradiation optical axis Li as
the light beam parallel to the irradiation optical axis Li. In this
case, the diameter of the objective lens group 26 is set to be
larger than the diameter of the outgoing light E.
[0039] The optical path forming optical system 12 includes a second
mirror 31, a third mirror 32, a fourth collimator lens 33, a cone
prism 34 and a third condensing lens 35, in order to obtain the
reflection light R reflected by the object.
[0040] The second mirror 31 is provided on the irradiation optical
axis Li behind the objective lens group 26 (on the side where the
double-sided mirror 30 is located). The second mirror 31 is
provided such that a flat reflection face 31 a becomes orthogonal
to the irradiation light axis Li, and reflects the reflection light
R of the reduced light beam in which the beam diameter is reduced
by the object lens group 26 toward the second reflection face 30b
of the double-sided mirror 30. Therefore, the diameter of the
second mirror 31 is set to be smaller than the diameter of the
objective lens group 26 and to be larger than the diameter of the
double-sided mirror 30. In addition, in the present embodiment, an
after-described half mirror for forming a collimation optical
system is used for the second mirror 31. The reflection light R
reflected by this second reflection face 30b is guided to the third
mirror 32. In the present embodiment, the (back) focal point of the
objective lens group 26 is located between the second reflection
face 30b and the third mirror 32, and the fourth collimator lens 33
is a convex lens.
[0041] The third mirror 32 reflects the reflection light R
reflected by the second reflection face 30b of the double-sided
mirror 30 toward the fourth collimator lens 33. The direction in
which the reflection light R travels after being reflected by the
second reflection face 30b and the axis line of the fourth
collimator lens 33 are the reflection optical axis Lr'. The cone
prism 34 and the third condensing lens 35 are provided on this
reflection optical axis Lr'. The incident end face 14b of the
light-receiving optical fiber 14 is disposed in the extended
position of the reflection optical axis Lr'.
[0042] The fourth collimator lens 33 converts the entered
reflection light R into a light beam parallel to the reflection
optical axis Lr'. Accordingly, the fourth collimator lens 33
functions as a reflection light collimator optical member in the
optical path forming optical system 12. The reflection light R
converted into the parallel light beam enters onto a convex side
end face 34a of the cone prism 34, and emits the reflection light R
as the parallel light beam having a reduced diameter from a concave
side end face 34b along the reflection light axis Lr' (refer to
FIG. 2). As illustrated in FIG. 2, the cone prism 34 includes a
rotationally symmetric circular cylindrical shape having the
reflection optical axis Lr' as a symmetrical axis. The convex side
end face 34a located on the fourth collimator lens 33 side is a
conical shape which projects to the fourth collimator lens 33 side.
The concave side end face 34b located on the third condensing lens
35 side is a conical shape which has a concave shape on the third
condensing lens 35 side (refer to FIG. 1). In addition, in the cone
prism 34, as seen from the cross-section surface including the
reflection optical axis Lr' (symmetrical axis), the convex side end
face 34a and the concave side end face 34b are set such that the
facing positions in the radial direction with the reflection
optical axis Lr' (refer to FIG. 3) at the center become parallel.
The function of this cone prism 34 will be described later.
[0043] The third condensing lens 35 is provided such that the
(back) focal position is located on the incident end face 14b of
the light-receiving optical fiber 14 as illustrated in FIG. 1, and
condenses the reflection light R of the parallel light beam emitted
from the concave side end face 34b of the cone prism 34, so as to
be entered on the incident end face 14b of the light-receiving
optical fiber 14. Accordingly, the third condensing lens 35
functions as the condensing optical member in the optical path
forming optical system 12. As described above, the third condensing
lens 35 condenses the reflection light R emitted from the concave
side end face 34b, so that the diameter (effective diameter) of the
third condensing lens 35 is set to be smaller than the diameter of
the fourth collimator lens 33. The reflection light R entered on
the incident end face 14b of the receiving optical fiber 14 is
guided to the light receiving and emitting mechanism 11 by the
light-receiving optical fiber as described above.
[0044] The optical path forming optical system 12 includes an
imaging lens 36, an imaging element 37, an image processor 38 and a
monitor 39, in order to observe the object (not shown). The imaging
lens 36 and the imaging element 37 are provided on the irradiation
optical axis Li behind the second mirror 31 (on the side opposite
to the side where the objective lens group 26 is located). The
imaging lens 36 focuses the light (including the reflection light R
from the object) which has transmitted the second mirror 31 of the
half mirror on the imaging element 37. If the light enters onto the
light-receiving surface of the imaging element 37, the imaging
element 37 outputs the electric signals according to the light
volume to the image processor 38. The image processor 38 generates
the image signals by appropriately processing the electric signals
output from the imaging element 37, and outputs this image signals
to the monitor 39. The monitor 39 displays an image according to
the image signals from the image processor 38. Consequently, the
irradiation optical axis Li can be easily directed to the object
(not shown) if the user of the electric distance meter 10 views the
display screen of the monitor 39. The user of the electric distance
meter 10 can observe the object (not shown) on the irradiation
optical axis Li. Therefore, the objective lens group 26 and the
imaging lens 36 function as the collimation optical system. The
collimation optical system, the imaging element 37, the image
processor 38 and the monitor 39 function as the collimation
device.
[0045] Accordingly, in the electric distance meter 10, the outgoing
light E emitted from the light source 15 of the light receiving and
emitting mechanism 11 is guided to the optical path forming optical
system 12 by the emission optical fiber 13, and emits the outgoing
light E as the parallel light beam on the irradiation optical axis
Li via the third collimator lens 27, the expander lens 28, the
first mirror 29, the first reflection surface 30a of the
double-sided mirror 30 and the objective lens group 26, so that the
object (not shown) of a measuring object located on the irradiation
optical axis Li can be irradiated by the outgoing light E. Namely,
in the optical path forming optical system 12, the emission optical
path (emission optical system) is formed by the third collimator
lens 27, the expander lens 28 and the first mirror 29 and the
double-sided mirror 30.
[0046] In this case, the reflection light R from the object (not
shown) enters onto the objective lens group 26 as a light beam
substantially parallel to the irradiation optical axis Li. In the
electric distance meter 10, the reflection light R entered onto the
objective lens group 26 enters onto the incident end face 14b of
the light-receiving optical fiber 14 via the second mirror 31, the
second reflection face 30b of the double-sided mirror 30, the third
mirror 32, the fourth collimator lens 33, the cone prism 34 and the
third condensing lens 35. More specifically, in the optical path
forming optical system 12, the reflection optical path
(light-receiving optical system) is formed by the second mirror 31,
the double-sided mirror 30, the third mirror 32, the fourth
collimator lens 33, the cone prism 34 and the third condensing lens
35.
[0047] In this case, in the electric distance meter 10, the
diameter of the objective lens group 26 is set to be larger than
the diameter of the outgoing light E, and the double-sided mirror
30 is provided on the irradiation optical axis Li behind the
objective lens group 26, so that a part of the reflection light R
entered onto the objective lens group 26, which corresponds to the
central portion of the irradiation optical axis Li provided with
the double-sided mirror 30 does not reach the second mirror 31.
Namely, the reflection light R to the second mirror 31 does not
have a central portion with the irradiation optical axis Li at the
center. This reflection light R without having the central portion
is reflected by the second mirror 31, the second reflection face
30b of the double-sided mirror 30 and the third mirror 32, and
reaches to the fourth collimator lens 33. The reflection light R
without having the central portion becomes the parallel light beam
along the reflection light axis Lr' by the fourth collimator lens
33. Therefore, the reflection light R entered onto the convex side
end face 34a of the cone prism 34 becomes the parallel light beam
(refer to Lu1 in FIG. 2) without having the central portion with
the reflection optical axis Lr' at the center. The reflection light
R of the parallel light beam without having the central portion
passes through the cone prism 34 as described later, so that the
reflection light R becomes the parallel light beam (refer to Lu2 in
FIG. 2) having the central portion, and reaches to the third
condensing lens 35.
[0048] Next, problems of a conventional electric distance meter
will be described. FIG. 4 provides a view illustrating one example
of an optical path forming optical system 12' of an electric
distance meter 10' according to a conventional configuration.
[0049] The optical path forming optical system 12' of the electric
distance meter 10' has a configuration basically similar to the
optical path forming optical system 12 of the electric distance
meter 10 according to the present invention except that the cone
prism 34 is not provided between the fourth collimator lens 33 and
the third condensing lens 35'. Therefore, in the optical path
forming optical system 12' illustrated in FIG. 4, reference numbers
which are the same as the reference numbers of the optical path
forming optical system 12 in FIG. 1 are applied to portions which
are the same as those in FIG. 1, so the descriptions thereof will
be omitted.
[0050] In the optical path forming optical system 12', the
reflection light R converted into the parallel light beam along the
reflection optical axis Lr' via the fourth collimator lens 33
reaches to the third condensing lens 35'. The reflection light R
converted into the parallel light beam is condensed by the third
condensing lens 35', and enters onto the incident end face 14b of
the light-receiving optical fiber 14. Therefore, the third
condensing lens 35' is required to condense the reflection light R
of the parallel light beam via the fourth collimator lens 33. For
this reason, the diameter (effective diameter) of the third
condensing lens 35' is set to be substantially equal to the
diameter of the fourth collimator lens 33.
[0051] In the optical path forming optical system 12', it is
necessary to use the third condensing lens 35' having a large
diameter compared to the third condensing lens 35 of the optical
path forming optical system 12 of the electric distance meter 10
according to the present invention. This will cause the increase in
the size of the electric distance meter 10' and also the increase
in the costs.
[0052] The third condensing lens 35' condenses the reflection light
R via the fourth collimator lens 33 such that the reflection light
R enters onto the incident end face 14b of the light-receiving
optical fiber 14. In this case, in order to reduce the distance
from the third condensing lens 35' to the incident end face 14b of
the receiving optical fiber 14, it is necessary to use the third
condensing lens 35' having a short focal length, i.e., a large NA
(numerical aperture stop). However, in a lens having a large outer
diameter (effective diameter), it is difficult to obtain a short
focal length, i.e., a large NA (numerical aperture stop).
Therefore, in the optical path forming optical system 12', the
distance from the third condensing lens 35 to the incident end face
14b of the light-receiving optical fiber 14 is increased compared
to the third condensing lens 35 of the optical path forming optical
system 12 of the electric distance meter 10 according to the
present invention.
[0053] Next, the function of the cone prism 34 of the electric
distance meter 10 according to the present invention will be
described with reference to FIGS. 2, 3.
[0054] The cone prism 34 deflects the traveling direction of the
parallel light beam Lu1 without having the central portion with the
reflection optical axis Lr' at the center toward the reflection
optical axis Lr' in the radius direction centering on the
reflection optical axis Lr', so as to convert the parallel light
beam Lu1 into the parallel light beam Lu2 having the central
portion with the reflection optical axis Lr' at the center. By this
function, the outer diameter of the parallel light beam Lu2 emitted
from the cone prism 34 becomes smaller than the outer diameter of
the parallel light beam Lu1 entered onto the cone prism 34. The
light volumes are substantially equal in the vicinity of the cone
prism 34.
[0055] As illustrated in FIG. 3, the light beam lua parallel to the
reflection optical axis Lr' enters into the cone prism 34 via the
convex side end face 34a, and travels in the cone prism 34 as the
light beam lub. In this case, the convex side end face 34a has a
conical shape projecting to the fourth collimator lens 33 side, so
that the light beam lub deflects toward the reflection light axis
Lr' by the convex side end face 34a. Here, where an angle (incident
angle) between the light beam lua and the vertical line p1
orthogonal to the convex side end face 34a is .alpha., and an angle
(refraction angle) between the light beam lub and the vertical line
p1 is .beta., incident angle .alpha.>refracting angle .beta. is
obtained because the cone prism 34 exists in the air.
[0056] This light beam lub travels in the cone prism 34 and reaches
to the concave side end face 34b. In this cone prism 34, as seen
from the cross-sectional surface including the reflection optical
axis Lr', as described above, since the convex side end face 34a
and the concave side end face 34b are set such that the facing
portions in the radial direction with the reflection optical axis
Lr' at the center become parallel, the vertical line p1 orthogonal
to the convex side end face 34a and the vertical line p2 orthogonal
to the concave side end face 34b become parallel. Therefore, the
light beam lub enters onto the concave side end face 34b at an
angle which is equal to the refraction angle .beta. in the convex
side end face 34a. The light beam emitted from the cone prism 34
deflects similar to the case when entering onto the cone prism 34.
Accordingly, the light beam lub entered onto the concave side end
face 34b at the incident angle .beta. inside the cone prism 34
becomes the light beam luc which is emitted outside the cone prism
34 from the concave side end face 34b at the refraction angle
.alpha.. In this case, the concave side end face 34b is set to a
conical shape having a concave shape on the third condensing lens
35 side, and the light beam lub deflects to separate from the
refraction optical axis Lr' by the concave side end face 34b.
Therefore, the light beam luc emitted from the concave side end
face 34b at the refraction angle .alpha. travels parallel to the
reflection optical axis Lr'.
[0057] The relationship between the emission and incident from and
onto the cone prism 34 is constant regardless of the incident
position onto the convex side end face 34a, and the light beam
entered onto the convex side end face 34a in the direction along
the reflection light axis Lr' emits in the direction along the
reflection optical axis Lr' from the concave side end face 34b
after being deflected to come close to the reflection optical axis
Lr'.
[0058] In this cone prism 34, the material (refractive index) and
the inclination angles of the convex side end face 34a and the
concave side end face 34b are set such that the inner end positions
i1, i2 (refer to FIG. 3) of the reflection light R (refer to
parallel light beam Lu1) without having the central portion entered
onto the objective lens group 26, reflected by the second mirror
31, the second reflection face 30b of the double-sided mirror 30
and the third mirror 32 and converted into the parallel light beam
by the fourth collimator lens 33 emit to correspond to the
substantial reflection optical axis Lr'.
[0059] Accordingly, the parallel light beam (refer to Lu1 in FIG.
2) without having the central portion converted into the parallel
light beam along the reflection optical axis Lr' by the fourth
collimator lens 33 becomes the parallel light beam (refer to Lu2 in
FIG. 2) having a small outer diameter and the central portion with
the reflection optical axis Lr' at the center by passing through
the cone prism 34. The cone prism 34 changes the cross-section
shape of the light beam (cross-sectional surface as seen in the
direction orthogonal to the traveling direction) at zero of the
deflection angle (transmission deflection angle) between the
traveling direction of the entering light beam and the traveling
direction of the emitting light beam, i.e., without generating a
transmission deflection angle.
[0060] In the electric distance meter 10 according to the present
invention, the following effects (1) to (5) can be obtained.
[0061] (1) In the electric distance meter 10, after the parallel
light beam (refer to Lu1 in FIG. 2) emitted from the fourth
collimator lens 33 is converted into the parallel light beam (refer
to Lu2 in FIG. 2) having a small outer diameter by the cone prism
34, the parallel light beam enters onto the third condensing lens
35, so that the outer diameter (effective diameter) of the third
condensing lens 35 can be a small diameter (effective diameter).
Therefore, compared to the conventional electric distance meter
(refer to 10' in FIG. 4), the electric distance meter can be
downsized, and the costs can be reduced.
[0062] (2) In the electric distance meter 10, after the parallel
light beam (refer to Lu1 in FIG. 2) emitted from the fourth
collimator lens 33 is converted into the parallel light beam (refer
to Lu2 in FIG. 2) having a small diameter by the cone prism 34, the
parallel light beam enters onto the third condensing lens 35.
Therefore, as illustrated in FIG. 5, if the third condensing lens
35'' having a small outer diameter and an NA (numerical aperture
stop) which is equal to that of the third condensing lens (refer to
35' in FIG. 4) of the conventional electric distance meter (refer
to 10' in FIG. 4) is used, the distance from the third condensing
lens 35'' to the incident end face 14b of the light-receiving
optical fiber 14 can be reduced compared to the conventional
electric distance meter (refer to 10' in FIG. 4).
[0063] (3) In the electric distance meter 10, after the parallel
light beam (refer to Lu1 in FIG. 2) emitted from the fourth
collimator lens 33 is converted into the parallel light beam (refer
to Lu2 in FIG. 2) having a small outer diameter by the cone prism
34, the parallel light beam enters onto the third condensing lens
35. Therefore, if the interval from the third condensing lens 35 to
the incident end face 14b of the light-receiving optical fiber 14
is set to be similar to that of the conventional electric distance
meter (refer to 10' in FIG. 4), the third condensing lens 35 having
a small outer diameter (effective diameter) and a long focal
length, i.e., a small NA (numerical aperture stop) can be used.
Accordingly, the electric distance meter 10 can be downsized
because the third condensing lens 35 is downsized, and the costs
can be reduced, compared to the conventional electric distance
meter (refer to 10' in FIG. 4).
[0064] (4) Since the third condensing lens 35 having a small outer
diameter (effective diameter) can be used compared to the
conventional electric distance meter (refer to 10' in FIG. 4), the
diameter of the light-receiving optical fiber 14 can be reduced
without reducing a spread angle (later discussion). This will be
described hereinbelow with reference to FIG. 6.
[0065] FIG. 6 is a view illustrating a relationship between the
third condensing lens 35 and the incident end face 14b of the
light-receiving optical fiber 14 by an optical view. In FIG. 6
CSAE-A, reference number f denotes a (back) focal length of the
third condensing lens 35, and reference number d denotes a diameter
of the light-receiving optical fiber 14. In FIG. 6 CASE-B,
reference number f denotes a focal length and d/2 denotes a
diameter. In FIG. 6 CASE-C, reference number f/2 denotes a focal
length and d/2 denotes a diameter.
[0066] At first, as illustrated in FIG. 6 CASE-A, the (back) focal
length of a third condensing lens 351 is denoted by reference
number f, and the third condensing lens 351 and a light-receiving
optical fiber 141 are provided such that the center of an incident
end face 141b of the light-receiving optical fiber 141 having a
diameter d is located in the (back) focal position. In this case,
the light-receiving optical fiber 141 has the diameter d, and an
upper end position e1 of the incident end face 141b condenses the
parallel light beam incident on the third condensing lens 351 at a
predetermined angle -.theta.1 (upper side as seen FIG. 6 from the
front is +) relative to the reflection optical axis Lr'. Similarly,
a lower end position e2 condenses the parallel light incident on
the third condensing lens 351 at a predetermined angle +.theta.1
relative to the reflection optical axis Lr'. For this reason, the
parallel light having an angle .theta.1 enters onto each of the
upper side and the lower side of the incident end face 141b of the
light-receiving optical fiber 141 with the reflection optical axis
Lr' at the center. The angle in which the upper side angle and the
lower side angle are combined is the spread angle, and in the
example illustrated in FIG. 6 CASE-A, the spread angle is
2.theta.1.
[0067] In this case, as illustrated in FIG. 6 CASE-B, if a third
condensing lens 352 similar to that in FIG. 6 CASE-A is used, and a
light-receiving optical fiber 142 having a diameter d/2 is used,
the diameter of an incident end face 142b becomes smaller than the
incident end face 141b in FIG. 6 CASE-A, so that the angle .theta.2
incident on each of the upper position e3 and the lower position e4
becomes smaller than the angle .theta.1 in FIG. 6 CASE-B. For this
reason, in the example illustrated in FIG. 6 CASE-B, the spread
angle 2.theta.2 becomes smaller than the spread angle 2.theta.1 in
FIG. 6 CASE-A.
[0068] In this case, as illustrated in FIG. 6 CASE-C, if a
light-receiving optical fiber 143 having the diameter d/2 similar
to that in FIG. 6 CASE-B is used, and a third condensing lens 353
having the (back) focal length f/2 is used, the angle .theta.3
incident on each of the upper end position e5 and the lower end
position e6 becomes equal to the angle .theta.1 in FIG. 6 CASE-A.
For this reason, in the example illustrated in FIG. 6 CASE-C, the
spread angle 2.theta.3=2.theta.1 is obtained, which is the same
spread angle in FIG. 6 CASE-A.
[0069] As described above, in a small diameter lens (effective
diameter), the focal length can be easily reduced compared to a
large diameter lens (effective diameter). In the electric distance
meter 10 of the present invention, the third condensing lens 35
having a small diameter (effective diameter) can be used, so that
the focal length can be easily reduced, compared to the
conventional electric distance meter (refer to 10' in FIG. 4).
Accordingly, the diameter of the light-receiving optical fiber 14
can be reduced without reducing the spread angle relative to the
light-receiving optical fiber 14.
[0070] In the light-receiving optical fiber 14 having a small
diameter, the volume can be reduced compared to an optical fiber
having a large diameter, so that the occupied area can be reduced,
and the curvature when curving can be increased. For this reason,
the handling ability can be significantly improved. Accordingly, in
addition to the use of the third condensing lens 35 having a small
outer diameter (effective diameter), the occupied area of the
light-receiving optical fiber 14 can be reduced, and the handing
ability can be significantly improved, so that the size of the
electric distance meter can be significantly reduced compared to
the conventional electric distance meter (refer to 10' in FIG.
4).
[0071] (5) The parallel light beam (refer to Lu1 in FIG. 2) without
having the central portion, which is converted into the parallel
light beam along the reflection optical axis Lr' by the fourth
collimator lens 33 passes through the cone prism 34, so that the
parallel light beam is converted into the parallel light beam
(refer to Lu2 in FIG. 2) having a small outer diameter and the
central portion with the reflection optical axis Lr' at the center.
Therefore, the reflection light R having the central portion can be
received by the incident end face 14b of the receiving optical
fiber 14, i.e., the light-receiving element 22 of the light
receiving and emitting mechanism 11.
[0072] (6) The cone prism 34 which converts the reflection light
converted into the parallel light beam without having the central
portion is converted into the parallel light beam having the
central portion by deflecting the reflection light on the optical
axis side in the radial direction includes the rotationally
symmetric cylindrical shape having the reflection optical axis Lr'
as a symmetrical axis in whole, the convex side end face 34a
located on the forth collimator lens 33 side includes the conical
shape projecting on the fourth collimator lens 33 side, and the
concave side end face 34b located on the third condensing lens 35
side includes the conical shape having the concave shape on the
third condensing lens 35 side, and the convex side end face 34a and
the concave side end face 34b facing each other in the radial
direction with the reflection optical axis Lr' at the center are
made of a single optical member such that the convex side end face
34a and the concave side end face 34b are set to be parallel to
each other. Accordingly, the cone prism 34 can be easily formed,
and the size can be easily reduced. Moreover, since the incident
light beam to the cone prism 34 and the outgoing light beam from
the cone prism 34 are converted into the parallel light beams
(refer to Lu1 and Lu2 in FIG. 2), respectively, the fourth
collimator lens 33 and the third condensing lens 35 can be provided
on the reflection optical axis Lr' such that the distance
therebetween is reduced. Therefore, the optical path forming
optical system 12 can be reduced; thus, the entire electric
distance meter can be easily downsized.
[0073] As described above, in the electric distance meter 10
according to the present invention, the third condensing lens 35
having a small outer diameter (effective diameter) can be used. In
addition, in the lens having a small outer diameter (effective
diameter), the focal length can be easily reduced, so that the
diameter of the light-receiving optical fiber 14 can be reduced
without reducing the spread angle to the light-receiving optical
fiber 14. The electric distance meter 10 can be thereby
downsized.
Modified Example
[0074] In the above embodiment, in the optical path forming optical
system 12, the emission end face 13b of the emitting optical fiber
13 connected to the light receiving and emitting mechanism 11 faces
the third collimator lens 27, and the incident end face 14b of the
light-receiving optical fiber 14 faces the third condensing lens
35, namely, the third collimator lens 27 side is the emission side
and the third condensing lens 35 side is the light-receiving side;
however, both of them can be interchanged.
[0075] In this modified example, an electric distance meter 100
will be described in which the emission end face 13b of the
emitting optical fiber 13 faces the third condensing lens 35, and
the incident end face 14b of the light-receiving optical fiber 14
faces the third collimator lens 27, the third condensing lens 35
side is the emission side and the third collimator lens 27 side is
the light-receiving side (refer to the emitting optical fiber 13
and the light-receiving optical fiber 14 illustrated in the dotted
line in FIG. 1).
[0076] Since this electric distance meter 100 is similar to the
electric distance meter 10 of the above-described embodiment except
for the connection relationship of the emitting optical fiber 13
and the light-receiving optical fiber 14 as described above, the
same reference numbers are applied to the same configurations, and
the description thereof will be omitted, Moreover, since the
electric distance meter 100 is similar to the electric distance
meter 10 of the above-described embodiment except for the
connection relationship of the emitting optical fiber 13 and the
light-receiving optical fiber 14, the operation in the light
receiving and emitting optical mechanism 11 is similar to that in
the electric distance meter 10, and the operation in the optical
path forming optical system 12 draws an optical path view similar
to that in the electric distance meter 100 except that the light
traveling direction becomes reversed by the reversing property of
light. Therefore, in the electric distance meter 100, reference
number R in FIG. 1 corresponds to the outgoing light and reference
number E in FIG. 1 corresponds to the reflection light.
Hereinafter, the outgoing light (R) and the reflection light (E)
are described. In the electric distance meter 100, the third
condensing lens 35 functions as an outgoing light collimator
optical member which converts the outgoing light (R) in the optical
path forming optical system 12.
[0077] In the electric distance meter 100, the outgoing light (R)
emitted from the light source 15 of the light receiving and
emitting mechanism 11 is guided to the optical path forming optical
system 12 by the emitting optical fiber 13. Then, the outgoing
light (R) is emitted as the parallel light beam on the irradiation
optical axis Li from the objective lens group 26 via the third
condensing lens 35, the cone prism 34, the fourth collimator lens
33, the third mirror 32, the second reflection face 30bo of the
double-sided mirror 30 and the second mirror 31. Therefore, in the
optical path forming optical system 12 of the electric distance
meter 100, the emission optical path is formed by the third
condensing lens 35, the cone prism 34, the fourth collimator lens
33, the third mirror 32, the both-sided mirror 30 and the second
mirror 31.
[0078] As described above, in the electric distance meter 100, the
object (not shown) of the measuring object located on the
irradiation optical path Li can be irradiated. If the distance from
the electric distance meter 100 to the object (not shown) is large
(the interval is significantly large to the optical system), the
reflection light (E) from the object enters onto the objective lens
group 26 as the light beam substantially parallel to the
irradiation optical path Li.
[0079] In the electric distance meter 100, a part of the reflection
light (E) entered onto the objective lens group 26, which has
reached the first reflection face 30a of the double-sided mirror 30
is reflected to the first mirror 29, and is entered onto the
incident end face 14b of the light-receiving optical fiber 14 via
the expander lens 28 and the third collimator lens 27.
Consequently, in the optical path forming optical system 12 of the
electric distance meter 100, the reflection optical path is formed
by the double-sided mirror 30, the first mirror 29, the expander
lens 28 and the third collimator lens 27.
[0080] Accordingly, in the electric distance meter 100, by
detecting the phase difference between the outgoing light (R)
emitted from the light source 15 and received by the
light-receiving element 22 and the reflection light (E) received by
the light-receiving element 22 via the optical path forming optical
system 12 and the initial phase of the outgoing light (R), or the
time difference from the emitting of the emission light (R) to the
receiving of the reflection light (E), the distance from the
electric distance meter 100 to the object (not shown) is calculated
by the calculator (not shown).
[0081] In the electric distance meter 100, the effects which are
similar to those in the electric distance meter 10 can be obtained.
Namely, a small outer diameter (effective diameter) of the third
condensing lens 35 (outgoing light collimator optical member) can
be obtained (the above-described effect (1)), the distance between
the third condensing lens 35 and the emission end face 13b of the
emitting optical fiber 13 can be reduced by using the third
condensing lens 35 having an NA (numerical aperture stop) which is
similar to the case when the cone prism 34 is not used (the
above-described effect (2)), the third condensing lens 35 having a
small diameter (effective diameter) and a long focal length, i.e.,
a small NA (numerical aperture stop) can be used if the distance
between the third condensing lens 35 and the emitting optical fiber
13 is set to be similar to the case when the cone prism is not used
(the above-described effect (3)), the diameter of the emitting
optical fiber 13 can be reduced without reducing the spread angle
(the above-described effect (4)), and the cone prism 34 can be
easily formed and the size can be easily reduced (the
above-described effect (6)). In addition, the effects associated
with those effects can be similarly obtained.
[0082] Moreover, in the electric distance meter 100, the outgoing
light (R) emitted from the emission end face 13b of the emitting
optical fiber 13 is converted into the parallel light beam along
the outgoing optical axis (refer to Lr'), and then is converted
into the parallel light beam (refer to Lu1 in FIG. 2) without
having the central portion. The outgoing light (R) without having
the central portion is guided to the objective lens group 26 via
the fourth collimator lens 33, the third mirror 32, the second
reflection face 30b of the double-sided mirror 30 and the second
mirror 31. Therefore, the double-sided mirror 30 exists in the
optical path from the second mirror 31 to the objective lens group
26, but the outgoing light (R) which passes through this optical
path does not have the central portion by the cone prism 34, and
the double-sided mirror 30 is located in the position without
having this central portion. Thereby, in the electric distance
meter 100, the outgoing light (R) emitted from the light source 15
is not kicked by the double-sided mirror 30 (the emission from the
objective lens group 26 is not shielded by the double-sided mirror
30), so that the volume of the outgoing light (R) emitted from the
light source 15 can be effectively used. When the light source 15
is constituted by the pulse laser diode (laser emission device) as
described in the present embodiment, the light intensity
distribution of the outgoing light is Gauss distribution. For this
reason, it is especially effective to remove the kicking of the
central portion about the optical axis in the outgoing light in
view of effectively using the light volume.
[0083] In the above embodiment, although the light receiving and
emitting mechanism 11 is constituted as illustrated in FIG. 1, the
mechanism 11 is not limited to the above-described embodiment as
long as the outgoing light E is emitted from the light source 15
and the reflection light R is received by the light-receiving
element 22 (light-receiving portion) in order to measure the phase
difference and/or the time difference from the emitting of the
outgoing light E to the receiving of the reflection light R.
[0084] In the above embodiment, the optical path forming optical
system 12 is constituted as illustrated in FIG. 1, but the optical
path forming optical system 12 is not limited to the above
embodiment as long as the emission optical path which emits the
outgoing light E from the objective lens group 26 on the
irradiation optical axis Li toward the object (not shown) is formed
and the reflection optical path which obtains the reflection light
R from the object entered onto the objective lens group 26 in a
state circularly surrounding the outgoing light E. This is the same
as the case when the light traveling direction becomes reversed by
interchanging the emission side and the reflection side in the
optical path forming optical system 12 (when the outgoing light E
and the reflection R are interchanged (modified example)).
[0085] In the above embodiment, the cone prism 34 includes the
rotationally symmetric cylinder shape having the reflection optical
axis Lr' as the symmetrical axis in whole, the convex side end face
34a located on the fourth collimator lens 33 side includes the
conical shape projecting to the fourth collimator lens 33 side, and
the concave side end face 34b located on the third condensing lens
35 side includes the conical shape having the concave shape on the
third condensing lens 35 side, and the convex side end face 34a and
the concave side end face 34b facing each other become parallel to
each other in the radial direction with the reflection optical axis
Lr' (symmetrical axis) at the center. However, these are not
limited to the shapes described in the above embodiment as long as
it can change the cross section shape of the light beam without
generating a transmittance deflection angle (cross section as seen
in the direction orthogonal to the traveling direction),
preferably, the reflection light converted into the parallel light
beam without having the central portion is converted into the
parallel light beam having the central portion by deflecting the
reflection light on the optical axis side in the radial
direction.
[0086] Although the electric distance meter of the present
invention has been described based on the above embodiments, the
present invention is not limited thereto. It should be appreciated
that variations may be made in the embodiments described by persons
skilled in the art without departing from the scope of the present
invention.
[0087] The present application is based on and claims priority from
Japanese Patent Application No. 2008-258732, filed on Oct. 3, 2008,
the disclosure of which is hereby incorporated by reference in its
entirety.
BRIEF DESCRIPTION OF THE DRAWINGS
[0088] FIG. 1 is a schematic view illustrating an optical system of
an electric distance meter according to the present invention.
[0089] FIG. 2 is a perspective view of a cone prism describing a
function of the cone prism for use in the electric distance
meter.
[0090] FIG. 3 is a sectional view illustrating the cone prism
including an optical axis (incident optical axis) for describing
the function of the cone prism.
[0091] FIG. 4 is a view illustrating one example of an optical path
forming optical system of a conventional electric distance
meter.
[0092] FIG. 5 is a schematic view illustrating an example in which
a focal distance of a third condensing lens of an optical path
forming optical system in the electric distance meter according to
the present invention is reduced.
[0093] FIG. 6 is a view in which an optical path view is applied to
the positional relationship between the third condensing lens and
the incident end face b of the light receiving optical fiber;
CASE-A illustrates an example in which the (back side) focal length
of the third condensing lens is f and the diameter of the light
receiving optical fiber is d; CASE-B illustrates an example in
which the focal length is f and the diameter is d/2; and CASE-C
illustrates an example in which the focal length is f/2 and the
diameter is d/2.
* * * * *